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1
Blood
Chapter 19
Introduction • Functions
– Transport medium – Regulation – Protection
• Composition – Plasma – fluid – Formed elements – cells & cell fragments
• Volume varies – Average = 5 liters
Human Anatomy, 3rd edition Prentice Hall, © 2001
Composition of Blood Plasma • = about 55% of the blood • Composition
– Mostly water – Plasma proteins – Dissolved foods, wastes, gases, ions
• Differences between plasma and intersititial fluid – Plasma has more dissolved gases – Plasma has more proteins – Concentrations of small molecules are similar
Plasma Proteins
• Most are made by the liver – Albumins – transport fatty acids & steroids – Globulins – immune functions – Fibrinogen – blood clotting
Formed Elements • Blood cells and cell fragments • Produced by hemopoiesis
– Arise from stem cells called hemocytoblasts • Types of formed elements
– Erythrocytes – red blood cells (RBCs) – Leukocytes – white blood cells (WBCs) – Thrombocytes – platelets
2
Human Anatomy, 3rd edition Prentice Hall, © 2001
Erythrocytes • Biconcave • Have no nuclei (or other
organelles) • Functional for about 120
days • Production occurs in the
red bone marrow – Erythropoiesis – Controlled by
erythropoietin • Functions
– Transport O2 & some CO2
Human Anatomy, 3rd edition Prentice Hall, © 2001
SEM of RBCs
Human Anatomy, 3rd edition Prentice Hall, © 2001
Hemoglobin
• Binds to oxygen & carbon dioxide
• Anemia • Polycythemia
(erythrocytosis)
Numbers of RBCs • Normally 4.3-5.8 million cells/mm3 of blood
– Males = 5.1-5.8 million/mm3
– Females = 4.3-5.2 million/mm3
• Numbers affect viscosity of blood • The percentage of erythrocytes, by volume, in
whole blood is the hematocrit – Males = 45% – Females = 42%
Leukocytes • About 5000 – 10,000/mm3 of blood • Produced by leukopoiesis in red bone marrow • Location – mostly in peripheral tissues • Functions
– Defense against pathogens – Removal of toxins, wastes, abnormal or damaged
cells • As large or larger than RBCs, contain nuclei
Types of WBCs
• Granulocytes have granules in their cytoplasm – Neutrophils – Eosinophils – Basophils
3
Human Anatomy, 3rd edition Prentice Hall, © 2001
A Neutrophil
• Neutrophils are phagocytic towards bacteria – 55-65% of circulating WBCs
Human Anatomy, 3rd edition Prentice Hall, © 2001
An Eosinophil
• Eosinophils are involved in allergic reactions and parasitic infections – 2-4% of circulating WBCs
Human Anatomy, 3rd edition Prentice Hall, © 2001
A Basophil • Basophils exaggerate inflammation at the site of
an injury – Less than 1% of circulating WBCs
Types of WBCs
• Agranulocytes do not have granules in their cytoplasm – Monocytes – Lymphocytes
Human Anatomy, 3rd edition Prentice Hall, © 2001
A Monocyte
• Monocytes are phagocytes and form the macrophages of the tissues – 2-8% of the WBC population
Human Anatomy, 3rd edition Prentice Hall, © 2001
A Lymphocyte
• Lymphocytes are responsible for specific immunity – B lymphocytes
produce antibodies – T lymphocytes
attack foreign cells directly
– 20-30% of the WBC population
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Human Anatomy, 3rd edition Prentice Hall, © 2001
Thrombocytes
• Formed from fragments of large cells called megakaryocytes
• Have no nuclei, lifespan is 10 – 12 days
• Number about 350,000/mm3 of blood
• Function – Involved in the clotting
mechanism
Human Anatomy, 3rd edition Prentice Hall, © 2001
Origins & Differentiation of Blood Cells
Human Anatomy, 3rd edition Prentice Hall, © 2001
Blood Types • Antigens are specific proteins on RBC membranes
– A, B, O, Rh • Antigens are accompanied by antibodies in plasma • Specific antibodies bind with antigens, cause agglutination